Lifting-jack.



I. E. HINDMAN.

LIFTING JACK.

APPLICATION FILED MAY 24, 1912.

LQMAl 3, Patented Feb. 25, 1913.

2 SHEETS-SHEEI 1.

I. E. HINDMAN.

LIFTING JACK.

APPLIGATION FILED MAY 24. 1912.

Patented Feb. 25, 1913.

'3 SHEETS-8HEET 2.

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-UNITED scrarwnntr OFFICE.

IAIAH E. HINDMAN, OF GRAFTON, PENNSYLVANIA, ASSIGNOR TO THE DUFF MANU-FACTURING COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OFPENNSYLVANIA.

LIFTING-JAGK.

Specification of Letters Patent.

Application filed May 24, 1912.

Patented Feb. 25, 1913.

Serial No. 699,417.

To all whom it may concern:

Be itknown that I, ISAIAH E. IIINDMAN, a resident of Grafton, in thecounty of Allegheny and State of Pennsylvania, have invented a new anduseful Improvement in Lifting-Jacks, of which the following is a full,clear, and exact description, reference being had to the accompanyingdrawings, forming part of this specification, in which- Figure 1 is avertical section showing a preferred form of my invention. Fig. 2 is across-section on the line II-II of Fig. 1. Fig. 3 is a partial sideelevation showing a controlling device. Fig. 4 is a perspective View ofthe controlling ring. Fig. 5 is a detail of one of the clutch rollers,and Fig. 6 is a vertical section on the line VI-VI of Fig. 2.

My invention has relation to lifting jacks; and is-more particularlyapplicable to jacks in which the lifting member when released will lowerrapidly under the weight of the load.

The invention is designed to provide a simple and eflicicnt fluid dashpot device for controlling the lowering movement.

In the accompanying drawing, I have shown the invention as applied to ahighspced screw jack of the type described and claimed in my co-pcndingapplication filed May 7th, 1912, Serial No. 695,729; but I desire it tobe understood thatthe present invention is not limited to use inconnection with this particular form of jack which is here shown for thepurposes of illustration.

In the drawings, 2 represents the base of the jack having an upwardlyprojecting cylinder 3 provided with a head 1 having a central nut 5. Thequick pitch screw stem 6 extends down through thcnut and has rotaryengagement with the piston 7 which is provided with 'a by-pass 8extending through it and controlled by an upwardly seating ball valve 9.

Surrounding the cylinder 3 is the lifting shell 10 which may have afoot-lift 11 at one side thereof, and carries at its top the liftingplate 12. Extending through a bearing 13 in the side of the shell is anoperating stud shaft 14 having a squared outer end 15 and carryingwithin the shell a bevel gear 16 intermeshing with horizontal bevel gear17, which is keyed to the threaded shaft 6. Surrounding the stem of thebevel gear 17 is a steel friction ring and ball race 18, having anannular groove in its upper face to receive a row .of balls 19 which arealso received by the corresponding annular groove in the upper ballbearing plate 20. This ball bearing plate 20 is centered by a reducedextension 21 by the elevating screw.

Outside the friction ring ,18, I place the controller 22, which is splitat an odd number of points, as shown at 23, to receive rollers 24. Theserollersare of greater diameter than the thickness of the ring and engagethe friction ring 18 within them and curved cam faces 25 outside them,and formed on the inner surface of a earn ring 25 which is forced intothe upper part of the shell with a press fit. There are, of course, asmany cam surfaces 25 as there are roll; ers or anti-friction elements24, and the cam faces are so positioned relative to the screw thread ofthe elevating screw that during lifting the friction of rotation tendsto carry the anti-friction elements into released position at thedeepest part of the cam grooves.

In order to cause the rollers, or anti-friction clutch devices to stopbackward movement and hold the load in any position to which it israised, some kind of biasing device is necessary which will constantlytend to more the parts into clutching position. In the form shown, Iaccomplish ,this by providing a stem or pin 26 which is secured to theupper enlarged diameter portion of the controller ring 22, and projectsoutward'ly through the shell. On this shell, '1 form a small casing 27,preferably by casting it integral with the casing, which contains aspring 28 surrounding the stem 29 of a bearing block 30 fitting theside' of the pin 26. The spring has a constant tendency to turn thecontroller ring in a clockwise direction, looking at Fig. 2, and henceto force the rollers into clutching position. This will not cause therollers to oppose the m tation in lifting, but will cause the rollerptoconstantly follow up the liftingmovement and always be ready to engageand check any backward movement. tice, it is found that no settling backcan be discerned when the lifting is stopped. Tliis In actual p amfeature is of great importance, because such jacks are usually operatedwith a ratchet lift and if a certain amount of lift is'lost' at eachstroke, this means a large reduction in 5 efliciency. The controllerring and clutch "device which I have just described may be used toadvantage with any rapid action screw jack having a screw of such apitch that the load will lower itself and the jack unless backwardmovement is stopped.

In this jack in order to lower it is only necessary to apply the reversedirection from that of lifting, which power will break the frictionconnection between the bevel gear 17 and its surrounding friction ring18, thus allowing the rotation inthe opposite direction and graduallylowering as desired' The parts are so designed that the friction betweenthe bevel gear and its friction ring can never be overcome by any loadwithin the range. of the jack, thus preventing any accidental droppingof the jack on to the load.

The jack as thus far described, is similar to that which forms thesubject-matter of my above referred to application. I will now describethe features which, constitute the present invention.

In order to provide for the regulating of the load, and without anymovement of the actuating gear, I provide the jack with a fluid dash potdevice, and also the knockofi device, which completely releases theclutch of the jack and allows the load to in the Hash pot. To this end Ifill the cylinder and bore of the casing with .oil up to about the levelshown in Fig. 1. The piston.

7, while provided with packing rings, nevertheless has a relativelyloose fit in the 1 cylinder, sothat under lowering pressure aconsiderable amount of oil will be forced around the piston and past'itspacking rings to permit descent of the outer shell. I also provide theby-pass passage 8 leading outwardly from inder and downwardly betweenthe cylinder and rail to the base of the jack, and connecting by a' port8 with the passage 8 leading into the lower portion of the cylinder. Ascrew'valve 8 isprovided to control the port 8 and thereby regulate theamount of oil which will flow through the passages 8 and 8 from one sideof the piston to. the other. In order to allow the load to force theshell downwardly, I also provide a knock-off device for the clutch rcontroller ring. In the form shown this coacts with 60 thebiasingdevice. It consists of a vertically movable wedge 31, having awedge face 32,

a straight face 33, and an engagement slot 34. This wedge slides withinsuitable slots in the casing 27, and the shell is provided with asuitable fulcrum or rest to receive.

5 down tinder the fluidfcontrol, the wedge is forced upwardlypinto theposit-ion shown in power to the shaft 14 in provides descend by leakageof the oil or other liquid.

' of jacks.

the upper port-ion'of the cyl-' a lever,. indicated in dotted lines at36, which may be engaged with the wedge. When it is desired to allow theload to move full lines in Fig. 3. This turns the controller ring to aposition where the. rollers are at the deepest parts of the cam groovesand are out ofaction ,.-and holds them in 1 this position. In this case,the friction ring will revolve as a part of the bevel wheel 17, and theload will push down the shells rapidly as the transfer of the fluid fromthe lower to the upper side of the piston will permit. During thelifting action the fluid will pass freely from above the pistonto belowthe same, since the ball valve 9 in the piston head will drop in itsseat.

It will benoted that the base is provided with the central hole, filledwith screw plug 37, in the construction shown, thus providing for theproper machining of the inner surface of thecylinder. The. oil may befilled in through a hole 38 in the top plate 12, which is closed by ascrew plug 39.

The advantages of my invention will be obvious to those skilled in theart, since it a simple dash pot device of an effective character,bymeans of which the load may be lowered, as may be desired, andthelowering action controlled to a nicety. While, as above indicated, myinvention is particularly applicable to high-speed lifting jacks of thecharacter described, it may obviously be adapted to various forms ofsuch jacks other than the particular ones shown, and is also applicableto other types I claim: v I

1. A high-speed lifting jack'having 21 screw stem,'a piston carriedthereby, a sta lionary member containing a cylinder and a nut bearingfor the screw stem,.a clutch device for holding the screw stem against.the action-of the load, and a knock-ofl device for the clutch, thecylinder and the piston having a-coiiperating fluid dash pot device forcontrolling the lowering movement of the screw stem when the knock-offdevice is'operated, substantially as described.

2. A lifting jack comprising a screw stem, a lifting head carriedthereby, a lifting-cylinder connected to the lifting head, a stationarycylinder finclosed by the lifting cylinder, and a piston carried by thescrew stem and working in the stationary cylinder, said piston andstationary cylinder hav-. ing a coiipcratin fluid dash pot device for'controlling the owering movement of the lifting member, substantially asdescribed.

3. A high-speed lifting jack, comprising an elevating screw, a pistoncarried thereby, a cylinder in which the piston is arranged to work, alifting cylinder connected to the lifting head and telescoping with thefirst '30 named cylinder, and a controllable bypass passage around thepiston in said cylinder,

.said nut having fluid substantially as described.

4. A lifting jack comprising an elevating screw, a piston carriedthereby, a cylinder in which the piston is arranged to Work, saidcylinder supporting a nut for the elevating screw, and cooperating dashpot devices carried by the piston and cylinder,

spaces thereln comn'uinicating with the fluid space of said cylinder,substantially as described;

5. A lifting jack comprising an elevating screw, a lifting head, alifting cylinder carried by said screw, a base carrying a stationarycylinder over which the lifting cylinder telescopically slides, gearingwithin said lifting cylinder for actuating the screw,

a nut carried by the stationary cylinder and engaging the screw, apiston carried by the screw and working in the stationary cylinder, andthe piston and the stationary cylinder having a fluid dash pot devicefor controlling the lowering movement of the screw, substantially asdescribed.

(3. A lifting jack comprising an elevating screw, means for actuatingthe screw, a fixed cylinder within which the lower portion of the screwextends, a piston carried by said screw and working in said cylinder,said piston having a port there-through, and an upwardly seating checkvalve controlling said port, and the cylinder having a bypass passageconnecting the upper and lower portions of the cylinder, and saidpassage having a controlling device, substantially as described.

7. A lifting jack comprising a lifting screw, a lifting head, a liftingcylinder carried by said screw, a base member havin a .40stationarycylinder over which the lifting cylinder telescopicallyslides, said stationary cylinder having a nut member engaging the screw,a piston carried by the screw and working within the stationarycylinder, said piston and stationary cylinder forming a dash pot devicefor controlling the lowering movement of the screw, the nut having afluid chamber therein communicating with the interior of said cylinder,and means for regulating the action of the dash pot device,substantially as described.

8. A lifting jack com rising a lifting screw, a lifting head, a 1i tingcylinder carried by said screw, and a base member having a stationarycylinder .with Which the lifting cylinder telescopes, there being aliquid space between a portion of the telescoping parts of -the saidcylinders, said space communicating with the interior of the first namedcylinder, and said piston and cylinder forming a dash pot device,substantially as described.

in testimony whereof, I have hereunto set my hand.

ISAIAII .E. HINDMAN.

lVitnesses:

(lino. ll. IAnnnLnn, ll. M. CORWIN.

